In many previous operations it has been the practice to mix and react a slurry of materials in a first vessel and then transfer the slurry mixture to a separate apparatus for drying and processing. This, of course, results in a duplication of equipment and time. The present invention incorporates a filter element in the mixing, reacting unit in such a manner as to markedly speed up the time it takes to go from the slurry stage to the friable condition and thus makes it possible to carry out mixing, reacting, washing and drying in a single vessel or chamber.
A search was conducted in the United States Patent Office in an effort to develop references which might show or suggest the invention. That search developed the patents listed below but no assertion is made that such references are indeed the closest prior art, although that was the intent of the search. These references disclose various filtering machines which appear to be separate from the mixing, reacting devices.
U.S. Pat. No. 3,365,065; Varjabedian PA0 U.S. Pat. No. 3,902,858; Chernykh PA0 U.S. Pat. No. 3,902,962; Reinhall PA0 U.S. Pat. No. 3,966,607; Gaynor et al. PA0 U.S. Pat. No. 4,003,837; Osborne PA0 U.S. Pat. No. 4,017,399; Lopker PA0 U.S. Pat. No. 4,081,381; Rosenmund et al. PA0 U.S. Pat. No. 4,159,953; Paquette PA0 U.S. Pat. No. 4,174,198; Kinoshita PA0 U.S. Pat. No. 4,178,246; Klein PA0 U.S. Pat. No. 4,217,220; Egli et al. PA0 U.S. Pat. No. 4,226,716; White PA0 U.S. Pat. No. 4,234,417; Gauld et al. PA0 U.S. Pat. No. 4,289,616; Hallack PA0 U.S. Pat. No. 4,315,820; Mann PA0 U.S. Pat. No. 4,347,134; Svehaug
Prior art mixing vessel design includes such apparatus and arrangements as a horizontal drum having a mixing element rotating about a horizontal axis, a vertical drum having mixing element rotation about a vertical axis, a vertical cone shaped vessel having vertical mixing elements rotating both about their own axes and about the inside circumference of the vessel, horizontal open trough type vessels having mixing element rotation about a horizontal axis, rotating vessels having fixed or rotating mixing elements with rotation being about a horizontal or vertical axis, and other devices as well. None of these, however, has incorporated a filter within the mixing vessel in the manner of the present invention so as to achieve mixing, reacting, washing and/or drying, or any combination of these, along with filtering, within that vessel in a continuous manner so as to bring the mixed materials from a slurry condition to a friable state.
Other prior art of interest, however, has also come to light. In addition to the earlier mentioned U.S. Pat. No. 3,027,102 Lodige et al, there are the U.S. Pat. Nos. 3,460,681 List et al, 2,521,121 Kilpatrick, 3,902,962 Reinhall, 1,382,056 Bontemps et al, 4,032,442 Peterson, 3,161,591 Petter et al, and 1,734,999 Cruickshank; in addition the disclosure in Chemical Engineers' Handbook, Perry & Chillon, Fifth Edition, Pages 19-69 to 19-72 is of interest. The more important of these references appear to be the patents to List et al and Kilpatrick in that they disclose some sort of filter in conjunction with some sort of mixing device, along with the Chemical Engineers' Handbook which discloses a filter of the general type which may be employed with this invention.